If you're at work and your co-workers won't stop chatting, there are two options: either tell them to go talk elsewhere or get a good pair of earplugs and/or headphones. If you've gone for the latter and can't seem to get over the concentration hump of focusing with music blaring, there's SimplyNoise, a white noise generator that runs right in your browser.
I've had a white noise loop kicking around on my iPod for years, and it doubles as a great way to get in the zone for napping. In SimplyNoise's case, you can dial in how much noise you want with a simple volume slider that's independent of your system volume. This works great in theory, but managed to crash my browser nearly every time I messed around with the slider, so your mileage may vary.
If you're looking to get a similar white noise experience on your computer, there's also a standalone player over on Download.com.